1. Field of the Invention
The present invention generally relates to a metal-insulator-metal capacitor for a metal damascene process and a method of manufacturing the same.
2. Description of the Related Art
Precision capacitors for complementary metal oxide semiconductor (CMOS) analog applications are generally metal-insulator-metal (MIM) capacitors or polysilicon-insulator-polysilicon (P-P) capacitors.
However, P-P capacitors are becoming less popular because they present a number of problems when used with complementary metal oxide semiconductor (CMOS) technologies. More specifically, P-P capacitors are generally performed before the CMOS structures and the heat and oxidation cycles which occur during the CMOS production process degrade the P-P capacitors. Further, the sophistication of analog circuits is improving which requires that the variation in the capacitance be decreased and preferably maintained at a voltage of approximately 25 ppM. However, P-P capacitors suffer from carrier depletion which changes the capacitance as surface voltage across the P-P capacitor changes. Therefore, P-P capacitors do not maintain the linearity required in today's sophisticated analog circuits. Further, P-P capacitors often trap charges within the insulator during their use.
Therefore, MIM capacitors, which are usually formed after the CMOS production process, are generally becoming more popular for analog circuits. However, MIM capacitors also present manufacturing problems. More specifically, conventional MIM capacitors with an SiO.sub.2 insulator cannot be used over copper damascene metal wiring because copper diffuses through the capacitor structure and creates leakage. In other words, the copper is not a good electrode in the conventional capacitor structures. Therefore, conventional MIM capacitors are generally only used with aluminum wiring. This is a substantial disadvantage because copper damascene wiring is becoming more popular in CMOS technologies because copper is less expensive and has better conductivity and electromigration resistance when compared to aluminum wiring.
Therefore, there is a need for a process and structure which allows MIM capacitors to be used with copper damascene wiring.